Flexible substrate

ABSTRACT

A flexible substrate includes a circuit board, a flexible heat-dissipating structure and an adhesive. The circuit board has a substrate and a circuit layer formed on a top surface of the substrate, and the flexible heat-dissipating structure has a flexible supporting plate and a flexible heat-dissipating metal layer formed on a surface of the flexible supporting plate. The flexible heat-dissipating metal layer of the flexible heat-dissipating structure is connected with a bottom surface of the substrate by the adhesive. The circuit layer and the flexible heat-dissipating metal layer are made of same material.

FIELD OF THE INVENTION

The present invention relates generally to a flexible substrate, andparticularly, to a flexible substrate with flexible heat-dissipatingstructure.

BACKGROUND OF THE INVENTION

Modern electronic products develop gradually toward light, thin, tinyand high performance to make the heat power of the electronic productsrising gradually. Conventional flexible substrate is made of lowthermal-conductive material so that the operation temperature ofelectronic products can not reduce quickly therefore affecting thestability of the electronic products.

SUMMARY

The primary object of the present invention is to provide a flexiblesubstrate. The heat-conductive efficiency of the flexible substrate isenhanced by a flexible heat-dissipating structure adhered to a circuitboard to make the flexible substrate with heat-dissipation function andhigh stability.

A flexible substrate of the present invention comprises a circuit board,a flexible heat-dissipating structure and an adhesive. The circuit boardcomprises a substrate and a circuit layer, wherein the substratecomprises a top surface and a bottom surface, the circuit layer isformed on the top surface, and the top surface comprises achip-disposing area. The flexible heat-dissipating structure isconnected with the bottom surface of the substrate and comprises aflexible supporting plate and a flexible heat-dissipating metal layer.The flexible supporting plate comprises a surface facing toward thebottom surface of the substrate, and the flexible heat-dissipating metallayer is formed on the surface of the flexible supporting plate. Theflexible heat-dissipating metal layer is located underneath thechip-disposing area and comprises a nickel-chromium alloy layer formedon the surface, a first copper layer formed on the nickel-chromium alloylayer and a second copper layer formed on the first copper layer. Theflexible heat-dissipating metal layer and the circuit layer are made ofsame material. The adhesive is formed on the second copper layer and thesecond copper layer is connected with the bottom surface of thesubstrate by the adhesive.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a manufacturing flow illustrating a flexible substrate inaccordance with an embodiment of the present invention.

FIG. 2A is a side-view diagram illustrating a circuit board inaccordance with the embodiment of the present invention.

FIG. 2B to 2E are manufacturing diagrams illustrating a flexibleheat-dissipating structure in accordance with a first embodiment of thepresent invention.

FIG. 2F is a side-view diagram illustrating the flexible substrate inaccordance with the first embodiment of the present invention.

FIG. 3 is a side-view diagram illustrating the flexible substrate inaccordance with a second embodiment of the present invention.

FIG. 4A is a side-view diagram illustrating the flexibleheat-dissipating structure in accordance with a third embodiment of thepresent invention.

FIG. 4B is a side-view diagram illustrating the flexible substrate inaccordance with the third embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIGS. 1 and 2A to 2E, a manufacturing method of aflexible substrate in accordance with a first embodiment includes step11 of providing a circuit board, step 12 of providing a flexibleheat-dissipating structure, step 13 of performing a cutting procedure,step 14 of providing an adhesive and step 15 of performing a stickingprocedure.

With reference to FIGS. 1 and 2A, providing a circuit board 110 in step11, the circuit board 110 comprises a substrate 111 and a circuit layer112 wherein the substrate 111 comprises a top surface 111 a and a bottomsurface 111 b, the circuit layer 112 is formed on the top surface 111 a,and the top surface 111 a comprises a chip-disposing area 111 c.

With reference to FIGS. 1, 2D and 2E, providing a flexibleheat-dissipating structure 120 in step 12, the flexible heat-dissipatingstructure 120 comprises a flexible supporting plate 121 and a flexibleheat-dissipating metal layer 122, wherein the flexible supporting plate121 comprises a surface 121 a, and the flexible heat-dissipating metallayer 122 is formed on the surface 121 a of the flexible supportingplate 121. The material of the flexible supporting plate 121 is selectedfrom polyimide (PI) or polyamic acid (PAA). In this embodiment, thematerial of the flexible supporting plate 121 is polyimide (PI).Preferably, the flexible supporting plate 121 and the substrate 111 aremade of same material, and the flexible heat-dissipating metal layer 122and the circuit layer 112 are made of same material.

With reference to FIGS. 2B to 2D, the flexible heat-dissipating metallayer 122 comprises a nickel-chromium alloy layer 122 a, a first copperlayer 122 b and a second copper layer 122 c. In this embodiment, thenickel-chromium alloy layer 122 a is formed on the surface 121 a of theflexible supporting plate 121 by sputtering, next, the first copperlayer 122 b is formed on the nickel-chromium alloy layer 122 a bysputtering, and the second copper layer 122 c is formed on the firstcopper layer 122 b by electro-plating therefore forming the flexibleheat-dissipating metal layer 122.

With reference to FIGS. 1, 2D and 2E, in step 13, the flexibleheat-dissipating structure 120 is cut by cutting tool (not shown inFig.), preferably, the area of the flexible heat-dissipating structure120 is not larger than the area of the circuit board 110. In thisembodiment, the flexible heat-dissipating metal layer 122 after cuttingcomprises a lateral surface 122 d, and the flexible supporting plate 121after cutting comprises a side wall 121 b coplanar with the lateralsurface 122 d.

With reference to FIGS. 1 and 2F, providing an adhesive 130 in step 14,the adhesive 130 is formed on the second copper layer 122 c of theflexible heat-dissipating metal layer 122. In this embodiment, thematerial of the adhesive 130 is 3M™ Adhesive Transfer Tape 467MP.

With reference to FIGS. 1 and 2F, in step 15, the flexibleheat-dissipating structure 120 is connected with the bottom surface 111b of the substrate 111, and the surface 121 a of the flexible supportingplate 121 faces toward the bottom surface 111 b of the substrate 111.The second copper layer 122 c of the flexible heat-dissipating metallayer 122 is connected with the bottom surface 111 b of the substrate111 by the adhesive 130 and the flexible heat-dissipating metal layer122 is located underneath the chip-disposing area 111 c. The flexibleheat-dissipating metal layer 122 with high heat-conducting efficiency isable to enhance the heat-conducting efficiency of the circuit board 110and a chip (not shown in Fig.) disposed on the chi-disposing area 111 c.

A flexible substrate 100 is formed by step 11 to 15 in the manufacturingmethod. The flexible substrate 100 comprises the circuit board 110, theflexible heat-dissipating structure 120 and the adhesive 130. Theflexible heat-dissipating structure 120 is connected with the substrate111 of the circuit board 110 by the adhesive 130 formed on the secondcopper layer 122 c. As a result of the substrate 111 of the circuitboard 110 and the flexible supporting plate 121 of the flexibleheat-dissipating structure 120 are made of same material, and thecircuit layer 112 of the circuit board 110 and the flexibleheat-dissipating metal layer 122 of the flexible heat-dissipatingstructure 120 are made of same material, so the thermal expansioncoefficient of the circuit board 110 and the flexible heat-dissipatingstructure 120 are similar. For the reason, the warping of the flexiblesubstrate 100 due to the difference thermal expansion level between thecircuit board 110 and the flexible heat-dissipating structure 120 isavoidable.

A second embodiment of the present invention is illustrated in FIG. 3.The primary difference between the second and the first embodiment isthat the flexible heat-dissipating structure 120 further comprises aprotecting layer 123 in the second embodiment. The protecting layer 123covers the lateral surface 122 d of the flexible heat-dissipating metallayer 122 and the bottom surface 111 b of the substrate 111. Theprotecting layer 123 is used to prevent metal ionization of the lateralsurface 122 d of the flexible heat-dissipating metal layer 122 fromoccurring. Preferably, the protecting layer 123 also covers the sidewall 121 b of the flexible supporting plate 121 to prevent the flexiblesupporting plate 121 from departing from the flexible heat-dissipatingmetal layer 122 and enhance the connecting strength between the flexibleheat-dissipating structure 120 and the circuit board 110.

A third embodiment of the present invention is illustrated in FIGS. 4Aand 4B. The primary difference between the third and the firstembodiment is that there is a space D between the lateral surface 122 dof the flexible heat-dissipating metal layer 122 and the side wall 121 bof the flexible supporting plate 121 in the third embodiment. The spaceD makes the surface 121 a of the flexible supporting plate 121 has anexposing surface 121 c not covered by the flexible heat-dissipatingmetal layer 122. The adhesive 130 covers the second copper layer 122 cof the flexible heat-dissipating metal layer 122 and the exposingsurface 121 c. When the flexible heat-dissipating structure 120 isconnected with the bottom surface 111 b of the substrate 111, the secondcopper layer 122 c and the exposing surface 121 c are connected with thebottom surface 111 b of the substrate 111 by the adhesive 130 to makethe flexible heat-dissipating metal layer 122 being sealed between theflexible supporting plate 121 and the substrate 111 thus preventingmetal ionization of the lateral surface 122 d of the flexibleheat-dissipating metal layer 122 from occurring and preventing theflexible heat-dissipating structure 120 from departing from the circuitboard 110.

While this invention has been particularly illustrated and described indetail with respect to the preferred embodiments thereof, it will beclearly understood by those skilled in the art that is not limited tothe specific features shown and described and various modified andchanged in form and details may be made without departing from thespirit and scope of this invention.

What is claimed is:
 1. A flexible substrate includes: a circuit boardcomprising a substrate and a circuit layer, wherein the substratecomprises a top surface and a bottom surface, the circuit layer isformed on the top surface, and the top surface comprises achip-disposing area; a flexible heat-dissipating structure connectedwith the bottom surface of the substrate comprising a flexiblesupporting plate, a flexible heat-dissipating metal layer and aprotecting layer, wherein the flexible supporting plate comprises asurface facing toward the bottom surface of the substrate and a sidewall, the flexible heat-dissipating metal layer is formed on the surfaceof the flexible supporting plate and located underneath thechip-disposing area, the flexible heat-dissipating metal layer comprisesa lateral surface coplanar with the side wall of the flexible supportingplate, and the protecting layer covers the lateral surface of theflexible heat-dissipating metal layer and the bottom surface of thesubstrate, wherein the substrate and the flexible supporting plate aremade of same material; and an adhesive formed on the flexibleheat-dissipating metal layer, wherein the flexible heat-dissipatingmetal layer is connected with the bottom surface of the substrate by theadhesive.
 2. The flexible substrate in accordance with claim 1, whereinthe material of the flexible supporting plate is selected from polyimideor polyamic acid.
 3. The flexible substrate in accordance with claim 1,wherein the protecting layer covers the side wall of the flexiblesupporting plate.
 4. The flexible substrate in accordance with claim 1,wherein the flexible heat-dissipating metal layer comprises anickel-chromium alloy layer formed on the surface, a first copper layerformed on the nickel-chromium alloy layer and a second copper layerformed on the first copper layer.
 5. The flexible substrate inaccordance with claim 4, wherein the adhesive is formed on the secondcopper layer.
 6. The flexible substrate in accordance with claim 4,wherein the circuit layer and the flexible heat-dissipating metal layerare made of same material.
 7. The flexible substrate in accordance withclaim 1, wherein the circuit layer and the flexible heat-dissipatingmetal layer are made of same material.